1. Field of the Invention
The present invention relates to a syringe and, more particularly, to a syringe having a needle which retracts upon a full depression of its plunger, rendering the syringe non-reusable.
2. Description of the Prior Art
Health care professionals who work in proximity to hypodermic needle type syringe devices are susceptible to accidental and potentially infectious contact with contaminated syringe needles resulting from careless handling and disposal of the same after use. Moreover, the spread of infectious diseases has reached epidemic proportions among users of controlled substances who exchange syringes. To combat the spread of disease on both fronts, there is a need to prevent both accidental needle strikes from as well as repeat usage of a syringe. This invention provides that protection automatically.
Several attempts have been devised to meet this end. For example, U.S. Pat. No. 2,571,653, issued Oct. 16, 1951 to Victor G. Bastien, discloses a syringe cover which may be snap-locked in an extended position after use to sheath the needle and offer protection against accidental needle strikes. The syringe cover proposed by Bastien must be extended manually as opposed to being automatically extended to sheath the needle. Moreover, this syringe cover may be retracted after use to expose the needle for reuse.
An automatically retractable syringe needle is disclosed in U.S. Pat. No. 3,306,290, issued Feb. 28, 1967 to Harold S. Weltman. Unlike applicant's instant invention, Weltman does not discloses a syringe in which the needle is conditionally fixed in an initially extended position where it can be covered with a protective cap. Further, Weltman does not disclose a needle which is retracted from the conditionally fixed position upon a full depression of the plunger and is retained in this retracted position so as to be non-reusable.
A syringe is disclosed in U.S. Pat. No. 3,672,368, issued Jun. 27, 1972 to Lothar Schwarz, wherein the syringe has a plunger for advancing a plug forward to empty a cartridge through a needle. An auxiliary plunger slides a needle forward into an operating position and an arresting device engages the needle to retain the needle in an advanced position. The actuating and auxiliary plungers are operated independent of one another. Further, the needle is not retractable and retained in a retracted position after use.
U.S. Pat. No. 3,890,971, issued Jun. 24, 1975 to Thomas A. Leeson et al., discloses a single-use syringe having a slidable needle cap which is mounted over the needle end of the barrel housing and is movable inwardly in order to expose the needle. A cap safety lock means is provided for moving the protective cap outwardly over the needle and locking the cap against further inward movement after the syringe has been used.
A shielded needle is disclosed in U.S. Pat. No. 4,631,057, issued Dec. 23, 1986 to Charles B. Mitchell, wherein the shielded needle comprises a body, a needle coupled to the body, and a needle guard mounted on the body for movement from a retracted position in which the guard does not shield the needle to an extended position in which the guard shields the needle. The guard can be releasably retained in the retracted position and locked in the extended position. Mitchell does infer that force can be applied to retract the needle guard after use and expose it for reuse.
A protective needle sheath is disclosed in U.S. Pat. No. 4,804,372, issued Feb. 14, 1989 to Joseph P. Laico et al. The sheath is manually extendable for protecting the sharpened needle point of a hypodermic needle. The sheath comprises a pair of telescopic enclosure shields mounted to the needle base. Detent locking members lock the shields in a non-retractable protective position.
Another single-use safety syringe in disclosed in U.S. Pat. No. 5,049,133, issued Sep. 17, 1991 to Joee A. Villen Pascual, who teaches a syringe provided with a needle and a spring coiled around the needle wherein the spring is capable of expanding upon a full depression of the plunger to retract the needle into the body of the syringe. The syringe includes means for retaining the needle in a position for use and for preventing the needle from moving after use. The plunger can be withdrawn to fill the barrel of the syringe, however, there exists no apparent means for limiting its withdrawal.
A movable shield member, disclosed in U.S. Pat. No. 5,061,251, issued Oct. 29, 1991 to Paul R. Juhasz, is interconnected to a syringe member to prevent accidental needle strikes when a syringe device is not in use. The shield member is manually movably to expose the needle and is spring biased to shield the needle.
Yet another single-use syringe is disclosed in U.S. Pat. No. 5,084,029, issued Jan. 28, 1992 to Carla Nacci nee Tagliaferri et al., wherein the syringe has a needle which retracts into the barrel of the syringe upon a depression of the plunger.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.